Brisant explosive charges and their manufacture



Patented Feb. 19, 1946 STATES FATE T @FFECE BRISANT EXPLOSIVE CHARGES AND THEIR MANUFACTURE James Taylor and Samuel Henry Davidson, Saltcoats, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application March 30, 1943, Serial No. 481,158. In Great Britain March 5, 1942 4 filaims.

- submarine or oil well blasting, and to the manulecture of explosive compositions containing a predominating proportion of trlnltrotoluene, and to the resulting improved or modified high density brisant explosive charges.

Trinltrotoluene explosive charges of high density are frequently produced either by pressing crystalised or other forms of trinitrotoluene, for which purpose very high pressures are required or by casting the molten or partly molten material into the container, and preferably sublecting the cast composition to a pressure higher than atmospheric before it solidifies. If it is allowed to solidify under atmospheric pressure cavities form in the material as it solidifies and the density does not exceed about 1.54 grammes per cubic centimetre. High density T. N. T. explosive. charges obtained by casting moreover require a comparatively large detonating impulse to cause them to propagate a high velocity detonation, and in practice a primer containing a considerable Weight of a more sensitive explosive composition has to be used to initiate them. Both the pressing and casting methods entail certain loading dlfllculties, and in particular it is difflcult to obtain the pressed charges except in simple shapes owing to the extremely high pressure required.

It has been proposed to facilitate the loading of shells and the like by making the trinitrotoluene into a crumbly plastic composition with.

plastic composition into the container. The resulting explosive charges, however, do not have a density exceeding about 1.5 and they are also comparatively insensitive to a detonating impulse, especially after storage.

The trinitrotoluene explosive charges made according to the present invention are compact solid masses having a very desirable combination of explosive properties, combining in pardenier a high density and. a high degree of insensitiveness to initiation by mechanical shock with a higher sensitiveness to initiation at high velocity by the impulse of a detonation than that of east trinltrotoluene charges at the same den- .aceording to the present invention, high densiiy brlsant explosive charges having the aforesaid desirable characteristics are prepared by milling together at ordinary temperatures ingredients adapted to form a mixture of substantially the'composition:

Per cent Explosive liquid nitric ester 15 to 20 Nitrocellulose in gelatinised conditlom- 0 to 7.5 Kieselguhr O to 5 Stabiliser 0 to 2.5 Trinitrotoluene Remainder until a powder mixture of aggregated particles is formed, and, before the mixture has lost its flowable properties, loading it into a container under tamping pressure.

By ordinary temperatures we mean temperatures at which the explosive liquid nitric ester is unfrozen, but not exceeding about 30 C.

If the liquid nitric ester consists of pure nitroglycerine the milling should be carried out at a temperature somewhat above atmospheric in cold weather, but atmospheric temperatures are usually quite suitable if low-freezing mixtures of nitroglycerine with nitroglycol or nitropolyglycerine are used. It will be understood that other explosive liquid nitric esters, for instance nitroglycerol chlorhydrin, or trlmethylol-nitromethane trinitrate may likewise be used in partial or complete substitution for nitroglycerine.

For the milling operation a machine such as an Atlas mixer in which only light pressure is exerted may be used. If necessary the bowl of the mixer can be provided with a jacket to enable it to be heated.

The liquid nitric ester is advantageously previously gelatinised with sufficient nitrocellulose to make it into a thin jelly, since its transport is thereby made safer, and depending on the viscosity characteristics of the nitrocellulose the amount required for this purpose may vary. The nitrocellulose is not especially effective in contributing to the valuable properties of the explosive charge and when nitrocellulose is used the type known as blasting soluble nitrocellulose is especially suitable since on account of its high viscosity only a small amount of it is required to form a jelly with the liquid nitric ester.

The trinitrotoluene is preferably crushed flake trinitrotoluene, but other ground or powder forms of trinltrotoluene may be used.

At the aforesaid ordinary temperatures saturated solutlons of trinitrotoluene in explosive liquid nitric esters are viscous liquids, but the explosive composition prepared according to our invention contains a considerable amount of undissolved trinitrotoluene. When freshly milled together its ingredients form a powder that can be tamped into containers of any de sired shape under quite moderate pressures to remarkably high densities, but on storage for several hours or days in the unpressed condition the powder binds together, forming a solid por ous cake that cannot easily be loaded to high densities and which is unsuitable for the military and other blasting purposes to which reference has already been made.

It will be understood that the larger the proportion of liquid trinitrotoluene solvent to trinitrotoluene in the freshly milled composition, the more readily does it tend to bind together, and accordingly when the proportion of liquid nitric ester 'or the temperature is near the upper limit it is especially useful to include kleselguhr in the composition as an absorbent for the liquid for the purpose of obtaining a freshly milled mixture of sumcient iriability to have the fiowable powder characteristics required to enable it to be loaded.

The stabiliser may be, for instance, mineral Jelly or an aryl ether or arylated nitrogen compound such as are us'ed'in the manufacture of propellent explosives as stabilisers, for example, beta-naphthyl methyl ether, phenyl benzyl urethane, ordi-ethyl-diphenyl urea.

The tamping of the powder into the container may conveniently be carried out at a pressure of 75 lbs. per square inch, at which pressure densities of 1.55 to 1.60 grams per cubic centimetre are easily attained. At such a density the resulting cast charge is sufliciently sensitive to be initiated at high velocity for instance 5000 to 6500 metres per second or more directly by a detonator not more powerful than a No. 8 Briska detonator, and it is not caused to detonate when backed by a steel plate and impacted by a 0.303 Mark VII British Army rifle bullet at 60 yards range.

A No. 8 Briska detonator contains a base charge of tetryl of 0.5 gm. pressed under a 1000 lbs. dead load, on which is superposed a further 0.25 gm. charge of tetryl pressed at about 20 lbs. dead load, and a top igniting charge amounting to 0.4 gm. pressed at 162 lbs. dead load consisting of a mixture of:-

Per cent Lead azide 64.8 Lead styphnate 27.6 Tetryl 4.8 Aluminium powder 2.8

all in an aluminium tube of internal diameter 5.75 mm. and external diameter 6.4 mm.

The invention is further illustrated by the following example, in which the parts are parts by weight.

assaees Example Parts Nitroglycerine i7 Blasting soluble nitrocellulose i Kieselguhr 1 Beta-naphthyl methyl ether 1 Crushed flake trinitrotoluene 80 The Jelly, made from the nitrocellulose and nitroglycerine, and the other ingredients are mixed together at a temperature of 12 to 20 C in an Atlas mixer for about ten minutes.

The

resulting powder is then transferred to the filling 1 house and is shaken and tamped under a pressure of 75 lbs. per square inch into containers. whereby it is converted into a solid cake, of density between 1.48 and 1.60.

While there have been described only a few embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore,

to be understood that the invention is not restricted to the details of the present disclosure otherwise than as defined in the appended claims.

We claim: 1. Process fonthe manufacture of high density brisant explosive charges'which comprises milling together at ordinary temperatures Parts by weight Explosive liquid nitric ester 15 to 20. Nitrocellulose 0 to 7.5 Kieselguhr 0 to 5 Stabiliser 0 to 2.5 Trinitrotoluene 85 to Per cent Explosive liquid nitric ester 15 to 20 Nitrocellulose in geiatinised condition- 0 to 7.5 Kieselguhr 0 to 5 Stabiliser 0 to 2.5 Trinitrotoluene Remainder having a bulk density not less than 1.55 grams per cubic centimetre.

JAMES TAYLOR.

SAMUEL HENRY DAVIDSON. 

